Search for the Higgs boson in the H → ZZ → 2l2ν channel in 1.6 fb−1

This is a condensed description with plots for the analysis CMS-HIG-11-016.

Abstract

A search for the Higgs boson in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 1.6 fb−1 recorded by the CMS experiment. The search is conducted in the decay channel H → ZZ → 2l2ν. No excess is observed in the transverse mass distributions. Limits are set on the production of the Higgs boson in the context of the Standard Model and in the presence of a sequential fourth family of fermions with high masses.

Main Results

We find no evidence of Standard Model Higgs boson production. We measure the 95% mean expected and observed C.L. upper limits on the cross section σ × BR( H → ZZ → 2l 2ν) for masses in the range 250 − 600 GeV/c2 . Results are obtained using a CLs approach with a flat prior for the cross section, for 1.6 fb−1 . We also measure the ratio R of the 95% C.L. cross section upper limit σ to the SM cross section, σSM as a function of the Higgs mass mH. With 1.6 fb−1 , the Standard Model Higgs with masses in the range 340 − 375 GeV/c2 can be excluded at 95% CL.

Results for the SM augmented with a 4th generation of particles are shown as well. This is the model in which the presence of another fermion family produces an enhancement of the dominant gluon-gluon fusion cross section. A scenario with fourth generation quark and lepton masses of 600 GeV/c2 is considered. With 1.6 fb−1 , Higgs masses in the range 250 − 550 GeV/c2 can be excluded at 95% CL.

Physics Analysis Summary

A note summarizing the analysis and the results can be found here: PAS

Figures

All public plots and tables from this analysis are collected here. Click on a figure to enlarge it, then double click to go to normal size again.

FIGURE	FILES	Description
	png, gif, pdf	Missing transverse energy distribution in the electron channel at pre-selection level for 1.6 fb−1 of data.
	png, gif, pdf	Missing transverse energy distribution in the muon channel at pre-selection level for 1.6 fb−1 of data.
	png, gif, pdf	DeltaPhi(MET,nearest jet) after pre-selection + MET cut in the electron channel for 1.6 fb−1 of data.
	png, gif, pdf	DeltaPhi(MET,nearest jet) after pre-selection + MET cut in the muon channel for 1.6 fb−1 of data.
	png, gif, pdf	Transverse mass of the LLNuNu system for the mH=250 GeV/c2 selection in the electron channel after all cuts except the MT-window cut, 1.6 fb−1 of data.
	png, gif, pdf	Transverse mass of the LLNuNu system for the mH=350 GeV/c2 selection in the electron channel after all cuts except the MT-window cut, 1.6 fb−1 of data.
	png, gif, pdf	Transverse mass of the LLNuNu system for the mH=250 GeV/c2 selection in the muon channel after all cuts except the MT-window cut, 1.6 fb−1 of data.
	png, gif, pdf	Transverse mass of the LLNuNu system for the mH=350 GeV/c2 selection in the muon channel after all cuts except the MT-window cut, 1.6 fb−1 of data.
	png, gif, pdf	Summary table of all systematic uncertainties on the final event yields in percent.
	png, gif, pdf	Summary table of the final yields for expected background and signal events, as well as observed events in 1.6/fb of data.
	png, gif, pdf	95% CL limit of the ratio of expected/measured cross section x BR over Standard Model for 1.6/fb of data.
	png, gif, pdf	95% CL limit of the ratio of expected/measured cross section x BR over Standard Model+4th generation extension for 1.6/fb of data.
	png, gif, pdf	Upper limit of the expected/measured cross section x BR for 1.6/fb of data.
	png, gif, pdf	Upper limit of the expected/measured cross section x BR assuming a 4th generation extension of the Standard Model, for 1.6/fb of data.
	png, gif, pdf	Event display of the highest transverse mass event in the muon channel analysis of 1.6/fb.
	png, gif, pdf	Event display of the highest transverse mass event in the muon channel analysis of 1.6/fb.
	png, gif, pdf	Event display of the highest transverse mass event in the muon channel analysis of 1.6/fb.

-- PetraMerkel - 19-Aug-2011